SORPTION OF INDAZIFLAM IN BRAZILIAN SOILS WITH DIFFERENT pH VALUES

ABSTRACT Pre-emergence herbicides, such as indaziflam, have agronomic efficiency when available in the soil solution, mainly in the superficial layer (0-10 cm), the region with the highest concentration of weed seed bank. However, information about the sorption of indaziflam in Brazilian soils still is scarce, since most studies available in the literature were conducted in soils of temperate regions. The objective of this study was to estimate the sorption of indaziflam using high-performance liquid chromatography (HPLC) and bioassay in a Latossolo Vermelho-Amarelo (Oxisol) and in a Cambissolo (Inceptisol), at pH values of 5.1 and 6.1. In the biossay, Sorghum bicolor was used as an indicator plant. Quantitative indaziflam data were obtained by HPLC, and the sorption and desorption coefficients were determined in the soils using Freundlich isotherms. Increasing the pH of the two soils from 5.1 to 6.1 resulted in reductions of C50 and sorption coefficient values. Desorption, a parameter estimated only by HPLC, showed an inverse behavior to that of sorption, that is, the lowest desorption was observed in the condition of highest sorption. It is concluded that the increase in pH of the studied soils reduces indaziflam sorption, influencing the recommendations of this herbicide, from both the agronomic and the environmental points of view. When the goal is to verify the presence or absence of indaziflam in the studied soils, the bioassay technique has satisfactory efficiency. Chromatographic assay is necessary when quantifying the concentration of this herbicide in the soil.

Antimicrobial Activities of Cymbopogon citratus and Ximenia Americana Leaf Extracts Against Some Selected Bacterial and Yeast Clinical Isolates

Increasing emergence of resistance to antibiotics by pathogenic microorganisms worldwide necessitates the need for finding new antimicrobial agents with minimal resistance and side effects. This study was carried out to investigate the phytochemical content and antimicrobial activities of two ethno-medicinal plants namely: Cymbopogon citratus and Ximenia Americana. Methanol and aqueous were used as solvent for a soxhlet and aqueous percolation extraction techniques to obtain the crude extracts of the named plant parts. Tannins, steroids, reducing sugars, tritapenoids and Flavonoids were found present in these plant extracts. GC-MS analysis done in this study indicates the presence of some basic phenolic compounds, such as; Cyclohexane-1-3,5-trione & 2-phenyl-1,4-benzopyrone, in the C. citratus extract and methyl guanidine & 3-meyhylheptyl acetate in the X. americana extract, which have been attributed with numerous antimicrobial effects onmicrobial pathogens. Using an agar well diffusion bioassay technique the C. citratus extracts shows; both the extracts are active against E. coli and P. aeroginosa. While X. americana extracts shows a higher activity against C. albican. However the MIC/MBC/MFC of all the extracts shows that known of the extracts has an active viability below 12.5µg/ml.

Trifluralin and Atrazine Sensitivity to Selected Cereal and Legume Crops

Soil-applied herbicides can persist in sufficient concentrations to affect the growth of crops in rotations. The sensitivity of wheat, barley, oat, lucerne and lentil to trifluralin and atrazine residues were investigated with three glasshouse experiments in 2018 and 2019. Each bioassay crop species was tested against different concentrations of trifluralin and atrazine in sandy soil using a full factorial design. Shoot and root parameters of the tested crop species were fitted in logistic equations against herbicide concentrations to calculate effective doses for 50% growth inhibition (ED50). Results revealed that both shoot and root parameters of all the test crop species were significantly affected by trifluralin and atrazine. Trifluralin delayed crop emergence at the lower concentrations examined, while higher concentrations prevented emergence entirely. Low concentrations of atrazine did not affect emergence but significantly reduced plant height, soil–plant analyses development (SPAD) index, shoot dry weight, root length, root dry weight and number of nodules of all the crop species. At high concentration, atrazine resulted in plant death. Legumes were found to be more sensitive than cereals when exposed to both trifluralin and atrazine treatments, with lucerne being the most sensitive to both herbicides, ED50 ranging from 0.01 to 0.07 mg/kg soil for trifluralin; and from 0.004 to 0.01 mg/kg for atrazine. Barley was the most tolerant species observed in terms of the two herbicides tested. Lucerne can be used to develop a simple but reliable bioassay technique to estimate herbicide residues in the soil so that a sound crop rotation strategy can be implemented.

Saflufenacil Dose-Response Curves Applied to Brazilian ‘Cerrado’ Soils

The objective of this study was to evaluate the phytotoxicity of saflufenacil in Brazilian Cerrado soils with contrasting properties. Experiments were performed in a factorial design. To quantify herbicide phytotoxicity, the bioassay technique was used and cucumber (Cucumis sativum) was selected as a test plant. A greater reduction of the dry mass was observed for bioindicator plants in comparison to others in the Typic Dystrophic Red Latosol. A rate of 11.76 g i.a. ha-1 was required to reach 50% reduction of the plant dry mass for this soil. Rates of 30.87; 44.10, and 119.56 g i.a. ha-1, respectively, are needed to achieve a 50% reduction of the plant dry mass in the Typic Acric Red Latosol, Typical Orthic Arenosols Quartzipsamment, and Washed Sand. The bioavailability of saflufenacil is affected by soil properties and therefore the soil type should be considered when deciding upon possible rates.

Residual Effect of Herbicides Applied in Unpuddled Transplanted Aman Rice on The Succeeding Crops Assessed by Bioassay Technique

The residual effect of eight herbicides (pendimethalin, pyrazosulfuron-ethyl, butachlor, pretilachlor, orthosulfamuron, acetochlor + bensulfuron methyl, butachlor + propanil and 2,4-D amine) was applied in unpuddled transplanted aman rice in aa weedy and a hand weeded controls, was evaluated for succeeding crops viz. wheat, lentil and sunflower by following bioassay technique. A study was conducted at Bangladesh Agricultural University, Mymensingh from November 2013 to January 2014 after harvest of unpuddled transplanted aman rice. All herbicides were imposed as weed management practice of unpuddled transplanted aman rice during July to August 2013. The experiment was laid out in a randomized complete block design (RCBD) with three replications. As a consequence, the residual effect of those herbicides on the succeeding wheat, lentil and sunflower crops was evaluated in term of germination, leaf chlorophyll content, seedling shoot length and dry matter. The results showed that seedling germination of all these succeeding crops in the herbicide treated plots did not differ significantly from those of weedy and hand weeded control plots. Moreover, leaf chlorophyll content, seedling shoot length and dry matter of wheat, lentil and sunflower were not adversely affected by any of the herbicide treatments imposed in aman rice. It was concluded that herbicides used in unpuddled transplanted aman rice had no residual effect on the germination and leaf chlorophyll content, seedling shoot length and dry matter of the succeeding wheat, lentil and sunflower crops.Bangladesh Agron. J. 2016 19(2): 95-103

Use of vegetative test systems in monitoring of the ecological status of water bodies of the Salgir river

The main objective of researches is the definition of the ecological status of water bodies of the Salgir River using bioassay technique. The main goal is to define the feasibility of using these waters for irrigation. For this purpose the base alignments were chosen on the river, exposed on different intensity of anthropogenic loads, and also the treated wastewater from sewerage facilities of Simferopol. The bioassay technique presented growing seeds of test plants in the studied waters and following comparison of the length of their root system with the same seedlings grown in the distilled water. Garden radish and garden cress seeds were chosen as test plants seeds. The phytotoxicity of the tested waters was shown in inhibition of the root system development of test plants. The root system in contact with the studied waters has been developing more slowly, what proves the presence of harmful substances in testing waters, and shows their toxic effect on the plants developing. The biggest sensitivity to pollutants showed the garden cress, which had the maximal inhibiting effect of roots development of 41.8%, in comparison to the monitoring in distilled water. The experiment showed the prospects of use of test plants, with their short-term exposure with the studied waters, as a reflective criterion for bioassay testing of pollution of the natural and treated sewage waters.